Low-Level Mercury

Special Considerations

Because field blanks are so important in establishing the credibility of low level mercury data, we require them even for grab samples. The results must be reported with permit compliance samples.

For laboratories to maintain their capabilities for low level mercury analyses, they, too, must control contamination sources. Because mercury tends to stick to surfaces, it's easy to contaminate the instrument simply by analyzing samples. Higher concentration samples (100 ng/L and above) should not be analyzed with cleaner samples unless the samples are diluted or there are sufficient wash steps between samples to assure that there is no carry over of mercury from one sample to the next.

Clients should resist the temptation to request low level detection limits for samples that aren't that clean. Moreover, it's important that laboratories be notified about samples that are expected to contain higher levels of mercury so the samples can be handled appropriately to avoid contaminating the instrument.

For more information about the mercury strategy and how it applies to WPDES permits, visit the permits website or contact Tom Mugan (608.266.7420).

For more information on the sources of mercury and mercury reduction efforts, contact Randy Case (608.267.7639).